Windows 7's default picture viewer manages all supported image types on your computer, allowing you to open any given file from one application. Additionally, you can customize more than one picture viewer for multiple image types, thus providing more flexibility in the way you handle available pictures. For example, you can set a particular program to open JPG files and a different application to open PNG files. These customization options are available from Windows 7's Default Programs settings.
Set Default Image Viewer
Click the "Start" button, and then click "Default Programs."
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Click "Set Your Default Programs." This option allows you to set a single program to open all supported image types on your computer.
Select the picture viewer, such as Paint or Windows Photo Viewer, you wish to set as the default program from the left pane.
Click "Set This Program as Default" to automatically set all supported image types to that specific application. Otherwise, click "Choose Defaults for this Program," and then toggle which image types you wish for that program to handle.
Click "OK" to save all changes.
Associate Image Types to Program
Click the "Start" button, and then select "Default Programs."
Click "Associate a File Type or Protocol With a Program." Use this option to set particular image types to specific programs.
Click to select the image type you wish to view with a different program, and then click "Change Program."
Select the program you wish to associate with the image type in question. Alternatively, select an application from the Other Programs section if you do not see the desired picture viewer, or click "Browse" to select another one from your computer.
Click "OK" to apply the new program as the default picture viewer for the selected image type. Perform the same steps for all other image types you wish to assign to a default program.
These changes only apply to your Windows user account.